The need for mild moisturizing skin cleansing compositions is well known and is made more acute by the general aging trend of the human population, as well as the ever increasing environmental insult to which skin is subjected. The mildest currently-available skin cleansing products can, at best, produce cleansing without negatively effecting the skin condition. To achieve an improvement in skin condition, the consumer is generally forced to use a second, separate product often called a moisturizer. The use of two separate products to achieve the desired skin state is inconvenient and often unpleasant due to the greasy skin feel which results from use of many moisturizers. As a result, many persons suffer from the effects of poor skin condition, rather than use two separate products. There is clearly a need for a single product which is capable of effectively delivering both mild skin cleansing and a skin conditioning benefit. This is particularly true in the case of older people since as skin ages it becomes thin, dry, itchy, fissured, and cracked, leaving areas particularly susceptible to dryness and irritation.
Many skin cleansing products contain humectant substances which, although effective when applied topically, are ineffective when delivered to the skin from a cleansing product. These humectants are ineffective because they are very water soluble and suffer from poor skin subtantivity. Hydrophobic emollient materials are generally more substantive to the skin, but are more difficult to incorporate into an aqueous skin cleansing matrix. There are at least two sources of difficulty which are typically encountered: poor lather effects and physically unstable products.
Petrolatum is a well-known occlusive moisturizer which would be desirable to incorporate into a bar soap formulation. However, this has been difficult to accomplish as a result of the very greasy and hydrophobic properties of the material. Particle size control has, in the past, been found to be important for the effective use of petrolatum in skin cleansing products.
U.S. Pat. No. 3,829,563, Barry, et al, issued Aug. 13, 1974, discloses a liquid skin cleansing composition containing 10 to 70% petrolatum having a particle size diameter smaller than 5 microns.
U.S. Pat. No. 5,312,559, Kacher, et al, issued May 17, 1994, describes a stable, mild soap personal cleansing and moisturizing composition which contains free fatty acid soap, free fatty acid, water, and large particle size (i.e., greater than about 45 microns) petrolatum. The composition may be formulated as a bar soap.
These and similar compositions tend to be difficult to formulate since they require very specific particle size limits in order to permit formulation and use. In addition, the physical characteristics of the petrolatum tend to detract from the cosmetic-acceptability of the compositions, as the material does not spread well when applied to the skin.
It has now been found that by incorporating certain specific types of emollients, especially hydroxylated milk glycerides, into bar soap compositions, formulations containing petrolatum, which provide several unexpected benefits to both the manufacturer and the user, can be provided. Specifically, the compositions of the present invention enhance spreading of the petrolatum on skin, making them cosmetically acceptable and eliminating the need for formulations which require specific particle size distributions for the petrolatum, as are disclosed in the Kacher, et al patent, discussed above. In addition, the compositions permit the inclusion of milk glyceride materials into higher pH products without having any significant degradation of those materials. Finally, the compositions of the present invention provide improved processing in that they minimize double stamping and provide soap bars having very clean stamped edges. These benefits are obtained without the need of using any additional release agents in the formula.
Japanese Patent Application 01-45309, published Feb. 17, 1989, describes a moisturizing toilet soap which contains 5-10% skim or defatted milk.
Great Britain Patent Specification 21,414, published Sep. 30, 1893, describes a soap having excellent emollient properties which contains milk, skim milk or buttermilk. See, also, Great Britain Patent Specification 7,854, published Jun. 21, 1890, and Great Britain Patent Specification 21,438, published Feb. 27, 1892.
U.S. Pat. No. 4,704,224, Saud, issued Nov. 3, 1987, describes the use of coconut fatty acid soap together with tallow fatty acid soap in a bar soap composition to produce rich lather. An 80:20 weight ratio of tallow:coconut soap is particularly preferred.
U.S. Pat. No. 5,002,680, Schmidt, et al, issued Mar. 26, 1991, describes mild skin cleansing aerosol mouse emulsions which are taught to effectively moisturize skin. Petrolatum may be used as a moisturizer in the formulation.
A Cremerol.TM. HMG trade brochure (published by Amerchol Corporation, dated July, 1994) describes Cremerol.TM., a stable hydroxylated milk glyceride, as an excellent emollient for use in skin creams and lotions. The brochure does not describe use of the material in soap or in combination with petrolatum. Cremerol.TM. is taught to be equivalent to petrolatum in terms of skin moisturizing efficacy while exhibiting superior cosmetic properties. Cremerol.TM. is also taught to have a high spreading coefficient such that a mixture of mineral oil with Cremerol.TM. increases significantly the spreading coefficient of the mineral oil.
A Glucam.TM. trade brochure (published by Amerchol Corporation) describes a family of alkoxylated glucose derivatives as effective humectants, moisturizers and emollients which may be used in a wide variety of cosmetics, toiletries and dermatologicals, including skin lotions and bar soaps.